Adventitious buds are subnormal buds found at points along the stem. They arise from latent or dormant buds in the leaf axils of the young stem and persist for an indefinite number of years within the cortical-cambial zone. They retain connection back to the pith by means of a stele- a bundle of water-conducting tissues also known as a bud trace. These buds can be activated at any time during the life of the tree in response to various stimuli; such a response leads to the development of an epicormic branch. Epicormic branches and adventitious bud clusters are treated together because the blemishes and defects they reflect are similar. Often they occur together, with the adventitious buds surrounding the epicormic branch.

Adventitious bud clusters, similar to those described but of different origin, also can arise at any time during the life of the tree. They often originate from wounding or bruising of the cambium but may develop independently of any mechanical action.

Significance: Underlying the epicormic branch scar is a knot surrounded by numerous tiny twig knots and possibly small bark pockets. The epicormic branch knot may not penetrate deeply into the wood. However, these epicormic branches along with the bud clusters may develop at intervals throughout the life of the tree and then become overgrown so that the defects they cause are found at several to many localities within the bole. Adventitious bud clusters and epicormic branches can develop independently of each other.

In veneer logs, epicormic branch stubs or knots and adventitious bud clusters are defects that degrade the log for face veneer. Neither of these excludes the log for cutting into plywood panel backs, corestock, or container veneer. Similar consideration excludes a log that contains several to many bud traces, even though the dormant or latent buds at their forward ends have not developed into epicormic branches. The bud traces degrade logs for use as fine face veneer.

In factory logs, epicormic branch knots and adventitious bud clusters prevent clear cuttings and are log grade defects. Unless the bud traces are large, there is always the chance that they will be within the board and not visible.

In standing trees, epicormic branch knots and adventitious bud clusters often lower timber quality even when other types of defect are not present. If they are found on merchantable trees, it is highly probable that they have occurred several times during the life of these trees and that the normal growth of wood and bark has concealed any evidence of them.